Abstract: Regional implications of the structural geology and tectonics at Chignecto Bay, Nova Scotia
Bibliographic record
Abstract
The Minas fault zone, a Paleozoic Appalachian terrane boundary, is an excellent example of a long lived zone of intense deformation of low metamorphic grade and signifi cant displacement. Current interpretations indicate dominant dextral transpression during the Acadian orogeny as Meguma docked against the Avalon terrane. This transpressive fault zone was later reactivated and acted as the locus for the opening of the Fundy and Minas basins during the initial fragmentation of Pangea in the Triassic. Chignecto Bay offers excellent along and across strike exposure of the Minas fault zone; from this a detailed tectonic history can be obtained. The principal rock unit is the Greville River Formation, the distal facies of a single alluvial fan-fl uviatile-lacustrine unit of the Late Devonian–Early Carboniferous Horton Group. Four folding episodes have been identifi ed; fi rst generation folds are tight and isoclinal, second generation folds are open and recumbent, third generation folds are upright, NW vergent with shallow fold axis. Transposition is a dominant deformation mechanism. The fi nal folding episode produced large-scale warps with dextral vergence which have an axial plane oblique to the fault trace. This sequence of folding suggests that there has been a progression in regional tectonics from early contractional deformation across the fault zone to one of dextral shear along the fault. Early Mesozoic NW transtensional reactivation of the fault zone produced the Minas and Fundy basins which are fi lled by the Fundy Group syn-rift sedimentary deposits and basalts. Adjacent to the fault is a zone of intense deformation in which transtensional displacement is localized. This area is dominated by sinistral and normal faulting resulting in calcite veining and brittle microstructures. The Wolfville Formation is in fault contact with the Greville River Formation and is characterized by normal and sinistral strike slip faults. This is anticipated in a transtensional regime. Fold orientations are consistent with dextral displacement, which may be a late stage response of the now passive Fundy and Minas basins to the continued spreading offshore as the Atlantic opens. The relative westerly position of Chignecto with respect to the direction of collision between Avalon and Meguma produces an east–west variation in deformation intensity and styles. This can account for some of the differences in the structures observed at Chignecto and Greville Bay. Chignecto Bay offers insight into the early folding history of the Greville River Formation, which contrasts with the exposure at Greville Bay where cyclical transposition has obliterated the early folding sequence. Clearly Chignecto offers the opportunity to increase our knowledge of the tectonic evolution of the Minas and Fundy basins.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".